[Johnboyas]

I recently purchased an SMC Pentax-M 50mm F1.7 and really love the quality. I use back button AF, I hold it down and get my subject in focus, hear the beep and see the center AF point light up (I have it set to single point center), take the picture, etc. Sometimes, and I'm not sure if it is always, the camera will beep multiple times even after I take the shot and release the AF button. Does this simply mean that once the camera is focused if I were to point it at some other subject the same distance away it will beep and light up the AF point in the VF letting me know that my subject is in focus?

[Rimfiredude]

You should not rely so much on the electronics. Focus, then press exposure button half way to check your focus. It will flash and beep if you are in focus. This will teach you to focus, rather that trusting the electronics. From an old manual focus guy that used to have good eyes.

[Johnboyas]

As I said, I'm using the back AF button and not the half-press shutter button method.

[Crowds]

As I said, I'm using the back AF button and not the half-press shutter button method.

I also use AF button to focus but on manual lenses while i press AF i had to move the ring till a beep sounds.
the several beeps came from usinf manual vs DSRL camera and the camera has some difficulties to "read" information. the way to get rid (sort of) of that is focusing veeery slowly.

either way...don't bother to much with that

[savoche]

I think Rimfiredude's point was that it would be a good thing to get used to not to rely on the focus confirmation when focusing manually - whether you have the AF linked to the shutter button or back button is less important in that context.

But to answer your question: My experience is that the AF sensors will stay active for a few seconds after you have let go of the AF button (or shutter button half press, if you have that linked to AF). It will then light up if something gets into focus during that period. (And beep as well, I suppose - I always turn off sound, so I can't confirm.)

[Johnboyas]

Thanks for the responses everybody.

[Not a Number]

With manual focus lenses there is no focus lock on the half-shutter press or with the AF button. So moving the focus spot will re-detect focus as long as the meter is active. If you have AF.S set the shutter will not release unless focus confirmation is indicated. This is great for catch in focus. However you can only select the center focus spot with manual focus lenses. This means you can't focus on one spot and recompose the shot as you will lose focus confirmation. I either set AF off or I have my AF button set to disable AF which allows the shutter to release without focus confirmation indicated.

[stevebrot]

This means you can't focus on one spot and recompose the shot as you will lose focus confirmation.

Thanks for mentioning this. I have been shooting manual focus lenses on Pentax dSLR ever since I got my K10D in 2007, but never explicitly considered this situation. I had encountered it, but just intuitively switched to MF mode so that I could have shutter release. (I almost never use CIF.)


Steve

[narual]

You're aware that the focusing screen that comes stock on the camera won't let you focus accurately at 1.7, right? You have to use LiveView zoomed in, or replace the focusing screen with a katzeye or ee-s or some other screen that's intended for manual focusing, not autofocus composition.

[aleonx3]

With manual focus lenses there is no focus lock on the half-shutter press or with the AF button. So moving the focus spot will re-detect focus as long as the meter is active. If you have AF.S set the shutter will not release unless focus confirmation is indicated. This is great for catch in focus. However you can only select the center focus spot with manual focus lenses. This means you can't focus on one spot and recompose the shot as you will lose focus confirmation. I either set AF off or I have my AF button set to disable AF which allows the shutter to release without focus confirmation indicated.

Are you using k-3 or k-5/IIs? The configuration setting is slightly different, as k-3 (there is AF1 mode and AF2 mode). In AF2 mode, the Half-press shutter does not activate AF, so basically negate CIF, but allow you to release shutter even though the previous focus point (using AF button) is no longer in focus. Typical use of AF2 is to use AF button to get focus point in focus (green hexagon) then move side way slight for re-composition, followed by shutter release. If you do it this way using manual focus lens, the degree of focus accuracy is in question as it depends much on how much you move side way to affect focus distance.